Microchip CAN Analyzer Road Test - part 3: Analyzer as Test Tool

I'm reviewing the Microchip CAN Analyzer for a Road Test. It'll be used in a CAN Bus that I'm designing. This blog shows that it is useful in a firmware design cycle.

The Analyzer as a Development Helper

In a previous CAN blog I wrote about configuring a Hercules microcontroller's CAN module. My setup is using interrupts to react on traffic and capture only relevant data.

The trigger should only fire when a message with ID == 1 appears on the CAN bus. Any other ID should be ignored. The CAN module should not interrupt the ARM controller.

An ideal scenario for the CAN Analyzer. I can use it to send a payload and choose an idea. It allows to generate messages to be captured and also ones to be ignored.

Here's the service routine:

#pragma WEAK(canMessageNotification)
void canMessageNotification(canBASE_t *node, uint32 messageBox)  
{
/*  enter user code between the USER CODE BEGIN and USER CODE END. */
/* USER CODE BEGIN (15) */
    if((node==canREG1)&& (messageBox == canMESSAGE_BOX1)) // transmit box
    {
      tx_done=1; /* confirm transfer request */
    }

    if((node==canREG1)&& (messageBox == canMESSAGE_BOX2)) // receive box
    {
     while(!canIsRxMessageArrived(canREG1, canMESSAGE_BOX2));
     canGetData(canREG1, canMESSAGE_BOX2, rx_ptr); /* copy to RAM */
     rx_ptr +=8;
    }
/* USER CODE END */
}

These lines of code are of interest here:

    if((node==canREG1)&& (messageBox == canMESSAGE_BOX2)) // receive box
    {
     while(!canIsRxMessageArrived(canREG1, canMESSAGE_BOX2));
     canGetData(canREG1, canMESSAGE_BOX2, rx_ptr); /* copy to RAM */
     rx_ptr +=8;
    }

canREG1 is there because we're working with CAN module 1 of the microcontroller (it has 2 of them).

canMESSAGE_BOX2 is the message box of that CAN module that we've configured as an inbound box,  listening to ID 1 only.

Test Scenarios

I've tested the following cases:

• trigger should not fire if ID is different than 1 (because I haven't defined a trigger for any other ID in the controller configuration).
• trigger should fire if ID is 1.
• if triggered, the following condition should evaluate TRUE:

if((node==canREG1)&& (messageBox == canMESSAGE_BOX2)) // receive box

• the payload should be copied to the controller's memory by the service routine
• send multiple messages.

All of the cases passed. Here's the result of a breakpoint firing after the first arrival of a message with ID == 1.

In the CAN Analyzer GUI, I set the ID to 1, the size to 8 bytes, and no repeats.

You can see that the Hercules stopped at the service routine's breakpoint, and copied the payload to the RAM:

     canGetData(canREG1, canMESSAGE_BOX2, rx_ptr); /* copy to RAM */

I'm showing the content of the first 8 bytes of that RAM buffer in the upper right of the capture. You can see that the values 1 -> 8 that I sent via the Microchip CAN analyzer are now in the RAM buffer.

In the past I have been testing these scenarios by programming another CAN enabled microcontroller.

The Analyzer makes this easier.